— Guess what? I happened to meet Fernando the other day.

— If my memory serves me correctly, you _____ each other for ages.[ ]

A. haven't seen

B. hadn't seen

C. didn't see

D. don't see

对头胎的孕妇进行随访观察，询问并记录她孕期的吸烟情况，而后研究分析吸烟史与新生儿低出生体重的联系，这种研究类型是：（）

A.临床试验

B.横断面研究

C.病例对照研究

D.队列研究

E.现况研究